Novel mechanisms and approaches in the study of neurodegeneration and neuroprotection. a review

Neurological Effects of Combining Low Toxic Dose of Tramadol and Nicotine: An Animal Model Evidence of Endoplasmic Reticulum Stress

Tramadol abuse is a common problem in the Middle East in conjunction with smoking. The current study applied immunohistochemistry, western blot, real-time PCR, and ELISA to test the combination toxicity. Low toxic doses of tramadol induced animal brain cortex inflammation and hippocampus injury. Adding nicotine reverted hippocampus pathological changes without triggering marked brain injury. The expression of CHOP protein with real-time PCR showed mild endoplasmic reticulum stress (ER) in rat's brain. Histological, immunohistochemical, and western blotting analysis of CHOP (CCAAT-enhancer-binding protein homologous protein) and BIP (immunoglobulin heavy chain-binding protein) chaperones demonstrated endoplasmic reticulum stress in the brains of animals. Furthermore, the levels of apoptosis and autophagy markers demonstrated a mild reaction. The blood level of serotonin was high in all study groups, with a marked increase in the combined one. The high serotonin levels in the blood can be critical and associated with a high risk of serious withdrawal and pathological consequences. Serotonin receptor blockers such as olanzapine may increase systemic serotonin levels and need further investigation to utterly pinpoint their roles in managing mood disorders. In conclusion, the combination of tramadol and nicotine is less harmful than expected. However, serious withdrawal effects can occur as a result of high systemic serotonin effects.

Prospective pilot study to explore the melatonin level in brain tumor patients undergoing radiotherapy

PURPOSE

Our aim was to assess if the radiotherapy dose decreased the melatonin levels as well as the quality of life and sleep in brain tumor patients.

METHODS

We performed a follow-up study on melatonin levels in saliva and its urinary metabolite sulfatoxi-melatonine (STM) samples in patients with brain tumors treated with radiotherapy close to the pineal gland's area. We analyzed the cortisol, cortisone, and excrection of STM normalized by urinary creatinine. In some cases, a polysomnography (PSG) was performed. Quality of life questionnaires, distress scale, and sleepiness inventories were also administered.

RESULTS

We included twelve patients (experimental arm) and eight healthy controls (control group). No differences were observed between experimental arm and control group at baseline. No differences were detected in the experimental arm before and after delivering the radiotherapy. No clinically significant differences were found according to the radiotherapy dose delivered.

CONCLUSION

Melatonin levels and PSG outcomes do not change after receiving radiotherapy. The findings of this study do not show a statistically significant association between the treatment and the quality of life and sleep.

Impact of smoking on course and outcome of aneurysmal subarachnoid hemorrhage

Background

While the smoking-related risk of experiencing an aneurysmal subarachnoid hemorrhage (aSAH) is well established, it remains unclear whether smoking has an unexpected “protective effect” in aSAH, or if smokers are more at risk for complications and poor outcomes.

Methods

Prospective, observational study investigating the course and outcome of aSAH in patients admitted during the years 2011 and 2012. Smoking status at admittance, demographic, medical, and radiological variables were registered along with management, complications, and outcome at 1 year in terms of mortality, modified Rankin score, and Glasgow outcome score extended. We compared current smokers with nonsmokers on group level and by paired analysis matched by aSAH severity, age, and severity of vasospasm.

Results

We included 237 patients, thereof 138 current smokers (58.2%). Seventy-four smoker/nonsmoker pairs were matched. Smokers presented more often in poor clinical grade, had less subarachnoid blood, and were younger than nonsmokers. Ruptured aneurysms were larger, and multiple aneurysms more common in smokers. Severe multi-vessel vasospasm was less frequent in smokers, whereas all other complications occurred at similar rates. Mortality at 30 days was lower in smokers and functional outcome was similar in smokers and nonsmokers. Poor clinical grade, age, cerebral infarction, and vertebrobasilar aneurysms were independent predictors of 1-year mortality and of poor functional outcome. Serious comorbidity was a predictor of 1-year mortality. Smoking did not predict mortality or poor functional outcome.

Conclusions

Notwithstanding clinically more severe aSAH, smokers developed less frequently severe vasospasm and had better outcome than expected. The risk for complications after aSAH is not increased in smokers.

Brain lipid profiles in the spontaneously hypertensive rat after subchronic real-world exposure to ambient fine particulate matter

Recent studies have illustrated an association between ambient fine particulate matter (PM_2.5) exposure and neuronal toxicity in epidemiological studies and animal models. However, the possible molecular effects on brains under real-world exposure to PM_2.5 remain unclear. In this pilot study, male spontaneously hypertensive rats were whole-bodily exposed to ambient air from the outdoor environment of Taipei City for 3 months, while the control rats inhaled HEPA-filtered air. The PM_2.5-induced phosphatidylcholine and sphingomyelin profiles in the hippocampus, cortex, medulla, cerebellum, and olfactory bulb were assessed by mass spectrometry (MS)-based lipidomics. Partial least squares discriminant analysis (PLS-DA) and the Wilcoxon rank sum test were used to examine the lipid changes between the exposed and control groups. The PLS-DA models showed that phosphatidylcholine and sphingomyelin profiles of the PM_2.5 exposure group were different from those of the control group in each brain region except the cortex. More lipid changes were found in the hippocampus, while fewer lipid changes were observed in the olfactory bulb. The lipid alteration in the hippocampus may strengthen membrane integrity, modulate signaling pathways, and avoid accumulation of lipofuscin to counter the PM_2.5-induced stress. The lipid changes in the cortex and medulla may respond to PM_2.5-induced injury and inflammation; while the lipid changes in the cerebellum were associated with neuron protection. This study suggests that the MS-based lipidomics is a powerful approach to discriminate the brain lipid profiles even at the environmental level of ambient PM_2.5 and has the potential to suggest possible adverse health effects in long-term PM_2.5 exposure studies.

High-throughput liquid chromatography mass-spectrometry-driven lipidomics discover metabolic biomarkers and pathways as promising targets to reveal the therapeutic effects of the Shenqi pill

Lipidomics, a branch of metabonomics, could provide a powerful technique for discovery of lipid molecules to reveal disease status and drug efficacy.

The Energy Homeostasis Principle: Neuronal Energy Regulation Drives Local Network Dynamics Generating Behavior

A major goal of neuroscience is understanding how neurons arrange themselves into neural networks that result in behavior. Most theoretical and experimental efforts have focused on a top-down approach which seeks to identify neuronal correlates of behaviors. This has been accomplished by effectively mapping specific behaviors to distinct neural patterns, or by creating computational models that produce a desired behavioral outcome. Nonetheless, these approaches have only implicitly considered the fact that neural tissue, like any other physical system, is subjected to several restrictions and boundaries of operations. Here, we proposed a new, bottom-up conceptual paradigm: The Energy Homeostasis Principle, where the balance between energy income, expenditure, and availability are the key parameters in determining the dynamics of neuronal phenomena found from molecular to behavioral levels. Neurons display high energy consumption relative to other cells, with metabolic consumption of the brain representing 20% of the whole-body oxygen uptake, contrasting with this organ representing only 2% of the body weight. Also, neurons have specialized surrounding tissue providing the necessary energy which, in the case of the brain, is provided by astrocytes. Moreover, and unlike other cell types with high energy demands such as muscle cells, neurons have strict aerobic metabolism. These facts indicate that neurons are highly sensitive to energy limitations, with Gibb's free energy dictating the direction of all cellular metabolic processes. From this activity, the largest energy, by far, is expended by action potentials and post-synaptic potentials; therefore, plasticity can be reinterpreted in terms of their energy context. Consequently, neurons, through their synapses, impose energy demands over post-synaptic neurons in a close loop-manner, modulating the dynamics of local circuits. Subsequently, the energy dynamics end up impacting the homeostatic mechanisms of neuronal networks. Furthermore, local energy management also emerges as a neural population property, where most of the energy expenses are triggered by sensory or other modulatory inputs. Local energy management in neurons may be sufficient to explain the emergence of behavior, enabling the assessment of which properties arise in neural circuits and how. Essentially, the proposal of the Energy Homeostasis Principle is also readily testable for simple neuronal networks.

Melatonin ameliorates Aβ1-42-induced Alzheimer's cognitive deficits in mouse model

Objectives

The objective of this study was to evaluate whether melatonin could ameliorate cognitive function in Aβ1-42-induced mouse model and its underlying mechanisms.

Methods

Series behaviour tests were performed to demonstrate the amelioration of cognitive function of the Alzheimer's disease (AD) mice induced by Aβ1-42. Additionally, enzyme-linked immunosorbent assay was applied to detect the expression of Aβ1-42, BACE1 and p-tau protein in the brain of the AD mice. JC-1 was performed to investigate the role in alleviating mitochondrial damage by melatonin in vitro. Western blot was used to detect the expression of melatonin on apoptosis-related factors caspase-3 and Bcl-2, as well as the expressions of GSK-3β and PP2A to further determine the mechanisms of melatonin on the expression of p-tau protein.

Key findings

Melatonin significantly ameliorated the cognitive function and mitochondrial damage in AD mice, reduced the expression levels of GSK-3β, caspase-3, Aβ1-42, BACE1, p-tau protein and increased the expressions of PP2A and Bcl-2.

Conclusion

From the overall results, we concluded that melatonin alleviated the mitochondrial damage effectively and decreased the expressions of the p-tau and some key proteins of apoptosis, leading to the improvement of cognitive function of the mice induced by Aβ1-42.

Therapeutic effects of ellagic acid on memory, hippocampus electrophysiology deficits, and elevated TNF-α level in brain due to experimental traumatic brain injury

OBJECTIVES

Cognitive defects such as learning and memory impairment are amongst the most repetitious sequelae after sever and moderate traumatic brain injury (TBI). It was suggested that ellagic acid (EA), an innate phenol product, display neuroprotective properties against oxidative and inflammatory damages after brain injury. The object of the current study was therapeutic properties of EA on blood-brain barrier (BBB) interruption and elevated content of TNF-α in brain tissue followed by neurologic aftereffects, cognitive and brain electrophysiology deficits as outcomes of diffuse TBI in rat.

MATERIALS AND METHODS

TBI was induced by a 200 g weight falling by a 2-m height through a free-falling tube onto the head of anesthetized rat. TBI rats treated immediately after trauma with EA (100 mg/kg, IP) once every 8 hr until 48 hr later. Neurologic outcomes, passive avoidance task (PAT), hippocampal long-term potentiation (LTP), BBB permeability and content of TNF-α in brain tissue were evaluated.

RESULTS

TBI induced significant impairments in neurological score, BBB function, PAT and hippocampal LTP in TBI+Veh group in compare with Sham+Veh (P<0.001). EA treatment decreased neurologic severity score (NSS), restored increased BBB permeability, cognitive and hippocampal LTP abnormalities, and elevated brain content of TNF-α due to TBI significantly (P<0.001).

CONCLUSION

Our findings propose that EA can restore NSS, cognitive and LTP deficits and prevent brain inflammation may by restore BBB permeability as well as lowering brain content of TNF-α following TBI.

An Overview of the Protective Effects of Chitosan and Acetylated Chitosan Oligosaccharides against Neuronal Disorders

Chitin is the second most abundant biopolymer on Earth and is mainly comprised of a marine invertebrate, consisting of repeating β-1,4 linked N-acetylated glucosamine units, whereas its N-deacetylated product, chitosan, has broad medical applications. Interestingly, chitosan oligosaccharides have therapeutic effects on different types of neuronal disorders, including, but not limited to, Alzheimer’s disease, Parkinson’s disease, and nerve crush injury. A common link among neuronal disorders is observed at a sub-cellular level, such as atypical protein assemblies and induced neuronal death. Chronic activation of innate immune responses that lead to neuronal injury is also common in these diseases. Thus, the common mechanisms of neuronal disorders might explain the general therapeutic effects of chitosan oligosaccharides and their derivatives in these diseases. This review provides an update on the pathogenesis and therapy for neuronal disorders and will be mainly focused on the recent progress made towards the neuroprotective properties of chitosan and acetylated chitosan oligosaccharides. Their structural features and the underlying molecular mechanisms will also be discussed.

Effect of Gallic Acid on Dementia Type of Alzheimer Disease in Rats: Electrophysiological and Histological Studies

INTRODUCTION

To study the effect of gallic acid (GA) on hippocampal long-term potentiation (LTP) and histological changes in animal model of Alzheimer disease (AD) induced by beta-amyloid (Aβ).

METHODS

Sixty-four adult male Wistar rats (300±20 g) were divided into 8 groups: 1) Control (Cont); 2) AD; 3) Sham; 4-7) AD+GA (50, 100, and 200 mg/kg for 10 days, orally) or vehicle, 8) Cont+GA100, Aβ (1μg/μL in each site) was infused into hippocampus bilaterally. Changes of amplitude and slope of LTP induced in hippocampal dentate gyrus (DG) were evaluated by high frequency stimulation (HFS) of perforant path (PP).

RESULTS

Data showed that LTP amplitude and area under curve significantly impaired in AD rats (P<0.001), while significantly improved in AD rats treated with GA (P<0.05, P<0.01).

CONCLUSION

Current findings suggest that GA reduces neural damage and brain amyloid neuropathology and improves cognitive function via free radicals scavenging and inhibiting oligomerization of Aβ but with no effect on healthy rats.

Effects of Chronic Low-Dose Radiation on Human Neural Progenitor Cells

The effects of chronic low-dose radiation on human health have not been well established. Recent studies have revealed that neural progenitor cells are present not only in the fetal brain but also in the adult brain. Since immature cells are generally more radiosensitive, here we investigated the effects of chronic low-dose radiation on cultured human neural progenitor cells (hNPCs) derived from embryonic stem cells. Radiation at low doses of 31, 124 and 496 mGy per 72 h was administered to hNPCs. The effects were estimated by gene expression profiling with microarray analysis as well as morphological analysis. Gene expression was dose-dependently changed by radiation. By thirty-one mGy of radiation, inflammatory pathways involving interferon signaling and cell junctions were altered. DNA repair and cell adhesion molecules were affected by 124 mGy of radiation while DNA synthesis, apoptosis, metabolism, and neural differentiation were all affected by 496 mGy of radiation. These in vitro results suggest that 496 mGy radiation affects the development of neuronal progenitor cells while altered gene expression was observed at a radiation dose lower than 100 mGy. This study would contribute to the elucidation of the clinical and subclinical phenotypes of impaired neuronal development induced by chronic low-dose radiation.

Cucurbitacins attenuate microglial activation and protect from neuroinflammatory injury through Nrf2/ARE activation and STAT/NF-κB inhibition

Emerging evidence suggests that neuroinflammatory responses are involved in the neuronal injury. Neuroinflammatory response is mediated by cellular components such as microglia and molecular components, including nitric oxide, prostaglandins and inflammatory cytokines, activation of complement proteins etc. Cucurbitacins is a class of highly oxidized tetracyclic triterpenoids isolated mainly from Cucurbitaceae but also from other plan families and has been reported to have pharmacological activities. The present study aimed to investigate the anti-neuroinflammatory effects of Cucurbitacins on TLR 2/4 agonists (amyloid-β, LTA, and LPS)-induced neuroinflammatory response in microglia and the underlying mechanism for Nrf2/ARE pathways. Results indicates that pretreatment with Cucurbitacins significantly reduced the pro-inflammatory cytokine (TNF-α, IL-1β and IL-6) and attenuated iNOS and COX-2 expression in TLR 2/4 agonists-stimulated microglia. In addition, Cucurbitacins inhibited JNK and p38 MAPKs activation and attenuated JAK-STAT and NF-κB activation in TLR 2/4 agonists-stimulated microglia. Next, we evaluate the potential involvement of Cucurbitacins in the activation of Nrf2/ARE signaling pathways and phase II detoxification enzymes activity. Results indicate that Cucurbitacins markedly promoted the activation of Nrf-2/ARE pathway-related downstream factors including NQO-1 and HO-1. Furthermore, anti-neuroinflammatory effects of Cucurbitacins are attenuated in the knockdown of Nrf2, HO-1 and NQO-1 respectively. Cucurbitacins also has neuroprotective effect against microglia over-activation related neuronal damage. This study demonstrates that Cucurbitacins is potent activator of the Nrf2/ARE pathway and is therapeutically relevant not only to neuroinflammatory responses of microglia but also neuroinflammation mediated neuronal injury.

Ellagic acid prevents cognitive and hippocampal long-term potentiation deficits and brain inflammation in rat with traumatic brain injury

AIMS

Traumatic brain injury (TBI) remains one of the main clinical problems globally and is a common cause of death among youth. Cognitive defects such as thinking, memory and behavior or mental health disorders are considered as the most frequent effects of severe and moderate TBI. It has been reported that ellagic acid (EA), a natural polyphenol, exhibits protective effects against oxidative damage. This study was performed to examine the EA preventive effects on cognitive impairments, long-term potentiation (LTP) deficits in hippocampus and brain inflammation induced by diffuse TBI in rat.

MAIN METHODS

Subchronic oral administration of 100 mg/kg EA, 7 consecutive days before induction of trauma (once daily) was used to elucidate the EA effects on passive avoidance memory and hippocampal LTP following TBI. To illustrate the possible mechanisms related to the preventive effects of EA on brain function following TBI, brain content of IL-1β, IL-6 and blood-brain barrier (BBB) permeability were determined.

KEY FINDINGS

EA pretreatment significantly (P<0.001) prevented TBI-induced memory and hippocampal LTP impairments in rat. Furthermore TBI induced elevation in brain content of IL-1β, IL-6 and BBB permeability were decreased significantly (P<0.001) due to EA pre-treatment.

SIGNIFICANCE

Our findings suggest that EA can prevent cognitive and LTP deficits and also prevent brain inflammation following TBI.

Activation of GSK-3β and caspase-3 occurs in Nigral dopamine neurons during the development of apoptosis activated by a striatal injection of 6-hydroxydopamine

The 6-Hydroxydopamine (6-OHDA) rat model of Parkinson's disease is essential for a better understanding of the pathological processes underlying the human disease and for the evaluation of promising therapeutic interventions. This work evaluated whether a single striatal injection of 6-OHDA causes progressive apoptosis of dopamine (DA) neurons and activation of glycogen synthase kinase 3β (GSK-3β) and caspase-3 in the substantia nigra compacta (SNc). The loss of DA neurons was shown by three neuron markers; tyrosine hydroxylase (TH), NeuN, and β-III tubulin. Apoptosis activation was determined using Apostain and immunostaining against cleaved caspase-3 and GSK-3β pY216. We also explored the possibility that cleaved caspase-3 is produced by microglia and astrocytes. Our results showed that the 6-OHDA caused loss of nigral TH(+) cells, progressing mainly in rostrocaudal and lateromedial directions. In the neostriatum, a severe loss of TH(+) terminals occurred from day 3 after lesion. The disappearance of TH(+) cells was associated with a decrease in NeuN and β-III tubulin immunoreactivity and an increase in Apostain, cleaved caspase-3, and GSK-3β pY216 in the SNc. Apostain immunoreactivity was observed from days 3 to 21 postlesion. Increased levels of caspase-3 immunoreactivity in TH(+) cells were detected from days 1 to 15, and the levels then decreased to day 30 postlesion. The cleaved caspase-3 also collocated with microglia and astrocytes indicating its participation in glial activation. Our results suggest that caspase-3 and GSK-3β pY216 activation might participate in the DA cell death and that the active caspase-3 might also participate in the neuroinflammation caused by the striatal 6-OHDA injection.

Dopaminochrome induces caspase-independent apoptosis in the mesencephalic cell line, MN9D

Parkinson's disease is characterized by a deficiency in motor cortex modulation due to degeneration of pigmented dopaminergic neurons of the substantia nigra projecting to the striatum. These neurons are particularly susceptible to oxidative stress, perhaps because of their dopaminergic nature. Like all catecholamines, dopamine is easily oxidized, first to a quinone intermediate and then to dopaminochrome (DAC), a 5-dihydroxyindole tautomer, that is cytotoxic in an oxidative stress-dependent manner. Here we show, using the murine mesencephalic cell line MN9D, that DAC causes cell death by apoptosis, illustrated by membrane blebbing, Annexin V, and propidium iodide labeling within 3 h. In addition, DAC causes oxidative damage to DNA within 3 h, and positive terminal deoxynucleotidyl transferase dUTP nick end labeling fluorescence by 24 h. DAC, however, does not induce caspase 3 activation and its cytotoxic actions are not prevented by the pan-caspase inhibitor, Z-VAD-fmk. DAC-induced cytotoxicity is limited by the PARP1 inhibitor, 5-aminoisoquinolinone, supporting a role for apoptosis-inducing factor (AIF) in the apoptotic process. Indeed, AIF is detected in the nuclear fraction of MN9D cells 3 h after DAC exposure. Taken together these results demonstrate that DAC induces cytotoxicity in MN9D cells in a caspase-independent apoptotic manner, likely triggered by oxidative damage to DNA, and involving the translocation of AIF from the mitochondria to the nucleus.

Anti-amyloidogenic and anti-apoptotic role of melatonin in Alzheimer disease

Alzheimer disease (AD) is an age-related neurodegenerative disorder characterized by the presence of senile plaques, neurofibrillary tangles and neuronal loss. Amyloid-β protein (Aβ) deposition plays a critical role in the development of AD. It is now generally accepted that massive neuronal death due to apoptosis is a common characteristic in the brains of patients suffering from neurodegenerative diseases, and apoptotic cell death has been found in neurons and glial cells in AD. Melatonin is a secretory product of the pineal gland; melatonin is a potent antioxidant and free radical scavenger and may play an important role in aging and AD. Melatonin decreases during aging and patients with AD have a more profound reduction of this indoleamine. Additionally, the antioxidant properties, the anti-amyloidogenic properties and anti-apoptotic properties of melatonin in AD models have been studied. In this article, we review the anti-amyloidogenic and anti-apoptotic role of melatonin in AD

Nicotine aggravates the brain postischemic inflammatory response

A substantial body of evidence suggests that nicotine adversely affects cerebral blood flow and the blood-brain barrier and is a risk factor for stroke. The present study investigated the effect of nicotine on cerebrovascular endothelium under basal and ischemia/reperfusion injury under in vivo condition. Nicotine (2 mg/kg sc) was administered to mice over 14 days, which resulted in plasma nicotine levels of ∼100 ng/ml, reflecting plasma concentrations in average to heavy smokers. An analysis of the phenotype of isolated brain microvessels after nicotine exposure indicated higher expression of inflammatory mediators, cytokines (IL-1β, TNF-α, and IL-18), chemokines (CCL2 and CX(3)CL1), and adhesion molecules (ICAM-1, VCAM-1, and P-selectins), and this was accompanied by enhanced leukocyte infiltration into brain during ischemia/reperfusion (P < 0.01). Nicotine had a profound effect on ischemia/reperfusion injury; i.e., increased brain infarct size (P < 0.01), worse neurological deficits, and a higher mortality rate. These experiments illuminate, for the first time, how nicotine regulates brain endothelial cell phenotype and postischemic inflammatory response at the brain-vascular interface.

Antiinflammatory activity of melatonin in central nervous system

Melatonin is mainly produced in the mammalian pineal gland during the dark phase. Its secretion from the pineal gland has been classically associated with circadian and circanual rhythm regulation. However, melatonin production is not confined exclusively to the pineal gland, but other tissues including retina, Harderian glands, gut, ovary, testes, bone marrow and lens also produce it. Several studies have shown that melatonin reduces chronic and acute inflammation. The immunomodulatory properties of melatonin are well known; it acts on the immune system by regulating cytokine production of immunocompetent cells. Experimental and clinical data showing that melatonin reduces adhesion molecules and pro-inflammatory cytokines and modifies serum inflammatory parameters. As a consequence, melatonin improves the clinical course of illnesses which have an inflammatory etiology. Moreover, experimental evidence supports its actions as a direct and indirect antioxidant, scavenging free radicals, stimulating antioxidant enzymes, enhancing the activities of other antioxidants or protecting other antioxidant enzymes from oxidative damage. Several encouraging clinical studies suggest that melatonin is a neuroprotective molecule in neurodegenerative disorders where brain oxidative damage has been implicated as a common link. In this review, the authors examine the effect of melatonin on several neurological diseases with inflammatory components, including dementia, Alzheimer disease, Parkinson disease, multiple sclerosis, stroke, and brain ischemia/reperfusion but also in traumatic CNS injuries (traumatic brain and spinal cord injury).

Nanotechnology applications and approaches for neuroregeneration and drug delivery to the central nervous system

Nanotechnology is the science and engineering concerned with the design, synthesis, and characterization of materials and devices that have a functional organization in at least one dimension on the nanometer (i.e., one billionth of a meter) scale. The potential impact of bottom up self-assembling nanotechnology, custom made molecules that self-assemble or self-organize into higher ordered structures in response to a defined chemical or physical cue, and top down lithographic type technologies where detail is engineered at smaller scales starting from bulk materials, stems from the fact that these nanoengineered materials and devices exhibit emergent mesocale and macroscale chemical and physical properties that are often different than their constituent nanoscale building block molecules or materials. As such, applications of nanotechnology to medicine and biology allow the interaction and integration of cells and tissues with nanoengineered substrates at a molecular (i.e., subcellular) level with a very high degree of functional specificity and control. This review considers applications of nanotechnology aimed at the neuroprotection and functional regeneration of the central nervous system (CNS) following traumatic or degenerative insults, and nanotechnology approaches for delivering drugs and other small molecules across the blood-brain barrier. It also discusses developing platform technologies that may prove to have broad applications to medicine and physiology, including some being developed for rescuing or replacing anatomical and/or functional CNS structures.

Impact of the CD40-CD40L dyad in Alzheimer's disease

As the number of elderly individuals rises, Alzheimer's disease (AD), marked by amyloid-beta deposition, neurofibrillary tangle formation, and low-level neuroinflammation, is expected to lead to an ever-worsening socioeconomic burden. AD pathoetiologic mechanisms are believed to involve chronic microglial activation. This phenomenon is associated with increased expression of membrane-bound CD40 with its cognate ligand, CD40 ligand (CD40L), as well as increased circulating levels of soluble forms of CD40 (sCD40) and CD40L (sCD40L). Here, we review the role of this inflammatory dyad in the pathogenesis of AD. In addition, we examine potential therapeutic strategies such as statins, flavonoids, and human umbilical cord blood transplantation, all of which have been shown to modulate CD40-CD40L interaction in mouse models of AD. Importantly, therapeutic approaches focusing on CD40-CD40L dyad regulation, either alone or in combination with amyloid-beta immunotherapy, may provide for a safe and effective AD prophylaxis or treatment in the near future.

Single-cell ELISA and flow cytometry as methods for highlighting potential neuronal and astrocytic toxicant specificity

The timeline imposed by recent worldwide chemical legislation is not amenable to conventional in vivo toxicity testing, requiring the development of rapid, economical in vitro screening strategies which have acceptable predictive capacities. When acquiring regulatory neurotoxicity data, distinction on whether a toxic agent affects neurons and/or astrocytes is essential. This study evaluated neurofilament (NF) and glial fibrillary acidic protein (GFAP) directed single-cell (S-C) ELISA and flow cytometry as methods for distinguishing cell-specific cytoskeletal responses, using the established human NT2 neuronal/astrocytic (NT2.N/A) co-culture model and a range of neurotoxic (acrylamide, atropine, caffeine, chloroquine, nicotine) and non-neurotoxic (chloramphenicol, rifampicin, verapamil) test chemicals. NF and GFAP directed flow cytometry was able to identify several of the test chemicals as being specifically neurotoxic (chloroquine, nicotine) or astrocytoxic (atropine, chloramphenicol) via quantification of cell death in the NT2.N/A model at cytotoxic concentrations using the resazurin cytotoxicity assay. Those neurotoxicants with low associated cytotoxicity are the most significant in terms of potential hazard to the human nervous system. The NF and GFAP directed S-C ELISA data predominantly demonstrated the known neurotoxicants only to affect the neuronal and/or astrocytic cytoskeleton in the NT2.N/A cell model at concentrations below those affecting cell viability. This report concluded that NF and GFAP directed S-C ELISA and flow cytometric methods may prove to be valuable additions to an in vitro screening strategy for differentiating cytotoxicity from specific neuronal and/or astrocytic toxicity. Further work using the NT2.N/A model and a broader array of toxicants is appropriate in order to confirm the applicability of these methods.

The antiapoptotic activity of melatonin in neurodegenerative diseases

Melatonin plays a neuroprotective role in models of neurodegenerative diseases. However, the molecular mechanisms underlying neuroprotection by melatonin are not well understood. Apoptotic cell death in the central nervous system is a feature of neurodegenerative diseases. The intrinsic and extrinsic apoptotic pathways and the antiapoptotic survival signal pathways play critical roles in neurodegeneration. This review summarizes the reports to date showing inhibition by melatonin of the intrinsic apoptotic pathways in neurodegenerative diseases including stroke, Alzheimer disease, Parkinson disease, Huntington disease, and amyotrophic lateral sclerosis. Furthermore, the activation of survival signal pathways by melatonin in neurodegenerative diseases is discussed.

Effects of lysophosphatidylcholine on beta-amyloid-induced neuronal apoptosis

AIM

We have investigated the effects of lysophosphatidylcholine (LPC), a product of lipid peroxidation, on Abeta(1-42)-induced SH-SY5Y cell apoptosis.

METHODS

The viability of cultured SH-SY5Y cells was measured using a CCK-8 kit. Apoptosis was determined by Chip-based flow cytometric assay. The mRNA transcription of Bcl-2, Bax, and caspase-3 were detected by using reverse transcription and real-time quantitative PCR and the protein levels of Bax and caspase-3 were analyzed by Western blotting. The cytosolic calcium concentration of SH-SY5Y cells was tested by calcium influx assay. G2A expression in SH-SY5Y cells was silenced by small interfering RNA.

RESULTS

Long-term exposure of SH-SY5Y cells to LPC augmented the neurotoxicity of Abeta(1-42). Furthermore, after LPC treatment, the Bax/Bcl-x(L) ratio and the expression levels, as well as the activity of caspase-3 were, elevated, whereas the expression level of TRAF1 was reduced. Because LPC was reported to be a specific ligand for the orphan G-protein coupled receptor, G2A, we investigated LPC-mediated changes in calcium levels in SH-SY5Y cells. Our results demonstrated that LPC can enhance the Abeta(1-42)-induced elevation of intracellular calcium. Interestingly, Abeta(1-42) significantly increased the expression of G2A in SH-SY5Y cells, whereas knockdown of G2A using siRNA reduced the effects of LPC on Abeta(1-42)-induced neurotoxicity.

CONCLUSION

The effects of LPC on Abeta(1-42)-induced apoptosis may occur through the signal pathways of the orphan G-protein coupled receptor.

Brain-region-specific astroglial responses in vitro after LPS exposure

Astroglia is well-known to be integrated in the complex regulation of neuroinflammation in the central nervous system. Astrocytes become activated and synthesize cytokines, chemokines, and prostanoids during degenerative and vulnerable processes and interact with other immune-competent cells. Degenerative disorders often occur in a brain-region-specific fashion suggesting differences in the activity and reactivity of innate immune cells. We have investigated the potency of lipopolysaccharides (LPS) to differently stimulate astrocytes from the cortex and midbrain. Astroglial cultures were prepared from Bagg albino/c mice and exposed to LPS. Astrocytes from both brain areas already differed in their capacity and profile of cytokine expression under basal unstimulated conditions. In response to LPS, we observed both a region-specific pattern of up-regulation of distinct cytokines and differences in the extent and time-course of activation. Our data demonstrate that astrocytes reveal a region-specific basal profile of cytokine expression and a selective area-specific regulation of cytokines upon LPS-induced inflammation. This makes astrocytes likely candidates to be responsible for region-specific incidence rates of neurological and neurodegenerative disorders.

Pomegranate polyphenols and resveratrol protect the neonatal brain against hypoxic-ischemic injury

A previous study from our lab has shown that the polyphenol-rich pomegranate juice can protect the neonatal mouse brain against hypoxic-ischemic (H-I) injury when given to mothers in their drinking water. To test the hypothesis that this protection is due to the polyphenols in the juice, we studied the effects of the pomegranate polyphenol extract in the same neonatal H-I model. To further explore the role of a specific polyphenol in neonatal H-I we investigated the effects of resveratrol. The neuroprotective effects of resveratrol have been demonstrated in adult models of stroke, but had not previously been examined in neonates. We show that pomegranate polyphenols and resveratrol reduce caspase-3 activation following neonatal H-I. Resveratrol reduced caspase-3 activation when given before the injury but not when given 3 h after the injury. In addition to preventing caspase-3 activation, resveratrol also reduced calpain activation. Finally, we show that resveratrol can protect against tissue loss measured at 7 days after the injury. These and other recent findings suggest that polyphenols should be further investigated as a potential treatment to decrease brain injury due to neonatal H-I.

Tea epigallocatechin-3-gallate increases 8-isoprostane level and induces caudal regression in developing rat embryos

Tea is the most common beverage after water. Concerns have been raised about the safety of tea during pregnancy, especially for embryo development. We aimed at studying the effects of active tea components on developing embryos by in vitro rat embryo culture. Rat embryos during early organogenesis were cultivated in serum supplemented with one of the tea catechins. Developmental hallmarks and malformations (Mal) in the developing embryos were compared and evaluated by a standard morphological scoring system. The embryotoxicity of each tea catechin was classified according to the European Center for the Validation of Alternative Methods. Cell viability was assessed by supervital dye staining, apoptosis by TUNEL assay, and peroxidation by the 8-isoprostane EIA method. We found that (+)-catechin had the least effect on developing embryos (Mal(50)=715.1 mg/L; IC50(Mal)=435 mg/L), whereas (-)-epigallocatechin gallate had the most adverse effect (Mal(50)=54.2 mg/L; IC50(Mal)=45.8 mg/L). The major malformation in affected embryos included caudal retardation with abnormal axial flexion and delayed hind-limb formation. All catechins were classified as nonembryotoxic except (-)-epigallocatechin gallate, which was classified as weakly embryotoxic. With (-)-epigallocatechin gallate, increased numbers of nonviable and apoptotic cells in the malformed embryos were associated with increased embryo 8-isoprostane.

Different mechanisms of lysophosphatidylcholine-induced Ca(2+) mobilization in N2a mouse and SH-SY5Y human neuroblastoma cells

In mice, lysophosphatidylcholine (LPC) was found to be a physiological substrate of neuropathy target esterase, which is also bound by organophosphates that cause a delayed neuropathy in human and some animals. However, the mechanism responsible for causing the different symptoms in mice and humans that are exposed to neuropathic organophosphates still remains unknown. In the present study, we examined and compared the effect of exogenous LPC on intracellular Ca(2+) overload in mouse N2a and human SH-SY5Y neuroblastoma cells. LPC caused an intracellular Ca(2+) level ([Ca(2+)](i)) increase in both N2a and SH-SY5Y cells; moreover, the amplitude was higher in N2a cells than that in SH-SY5Y cells. Preincubation of the cells with verapamil, an L-type Ca(2+) channel blocker, did not affect the LPC-induced Ca(2+) increase in N2a cells, verapamil inhibited the response by 23% in SH-SY5Y cells. In Ca(2+)-free medium, LPC produced a significant [Ca(2+)](i) decrease in N2a cells, while it caused 64% of total [Ca(2+)](i) increase in SH-SY5Y cells. The results of a cell viability test suggest that N2a cells were more sensitive to LPC than were SH-SY5Y cells. These data suggested that the LPC-induced [Ca(2+)](i) increase was produced in each cell line through different mechanisms. In particular, the [Ca(2+)](i) increase occurred via entry through a permeabilized membrane in N2a cells, but through L-type Ca(2+) channels as well as by Ca(2+) release from intracellular Ca(2+) stores in SH-SY5Y cells. Thus, the symptomatic differences of organophosphate-induced neurotoxicity between mice and humans are probably not related to the diverse amplitudes of intracellular Ca(2+) overload produced by LPC. Moreover, the demyelination effect induced by LPC in mice may be a consequence of its detergent effect on membranes.

Application of nicotine enantiomers, derivatives and analogues in therapy of neurodegenerative disorders

This review gives a brief overview over the major aspects of application of the nicotine alkaloid and its close derivatives in the therapy of some neurodegenerative disorders and diseases (e.g. Alzheimer's disease, Parkinson's disease, Tourette's syndrome, schizophrenia etc.). The issues concerning methods of nicotine analysis and isolation, and some molecular aspects of nicotine pharmacology are included. The natural and synthetic analogues of nicotine that are considered for medical practice are also mentioned. The molecular properties of two naturally occurring nicotine enantiomers are compared--the less-common but less-toxic (R)-nicotine is suggested as a natural compound that may find its place in pharmaceutical practice.

In vivo tomographic imaging studies of neurodegeneration and neuroprotection: a review

Noninvasive tomographic imaging methods including positron emission tomography (PET) and single photon emission computed tomography (SPECT) are extremely sensitive and are capable of measuring biochemical processes that occur at concentrations in the nanomolar range. Inherent to neurodegenerative processes is neuronal loss. Thus, PET or SPECT monitoring of biochemical processes altered by neuronal loss (changes in neurotransmitter turnover, alterations in receptor, transporter or enzyme concentrations) can provide unique information not attainable by other methods. Such imaging techniques can also be used to longtitudinally monitor the effects of neuroprotective treatments. This review highlights current imaging probes used to evaluate patients with specific neurodegenerative disorders (e.g., Alzheimer's Disease, Parkinson's Disease, Huntington's Chorea), including those that image receptors of the dopaminergic, cholinergic and glutamatergic systems. Areas of future research focus are also defined. It is clear that monitoring the progression of neurodegenerative disorders and the impact of neuroprotective treatments are two different but related goals for which noninvasive imaging via PET and SPECT methods plays a powerful and unique role.

Melatonin and anesthesia: a clinical perspective

The hypnotic, antinociceptive, and anticonvulsant properties of melatonin endow this neurohormone with the profile of a novel hypnotic-anesthetic agent. Sublingually or orally administered melatonin is an effective premedicant in adults and children. Melatonin premedication like midazolam is associated with sedation and preoperative anxiolysis, however, unlike midazolam these effects are not associated with impaired psychomotor skills or the quality of recovery. Melatonin administration also is associated with a tendency toward faster recovery and a lower incidence of postoperative excitement than midazolam. Oral premedication with 0.2 mg/kg melatonin significantly reduces the propofol and thiopental doses required for loss of responses to verbal commands and eyelash stimulation. In rats, melatonin and the more potent melatonin analogs 2-bromomelatonin and phenylmelatonin have been found to have anesthetic properties similar to those of thiopental and propofol, with the added advantage of providing potent antinociceptive effects. The exact mechanism(s) by which structurally diverse intravenous and volatile anesthetics produce general anesthesia is still largely unknown, but positive modulation of gamma-aminobutyric acid type A (GABAA) receptor function has been recognized as an important and common pathway underlying the depressant effects of many of these agents. Accumulating evidence indicates that there is interplay between the melatonergic and GABAergic systems, and it has been demonstrated that melatonin administration produces significant, dose-dependent increases in GABA concentrations in the central nervous system. Additional in vitro data suggest that melatonin alters GABAergic transmission by modulating GABAA receptor function. Of greater importance, data from in vivo studies suggest that the central anesthetic effects of melatonin are mediated, at least in part, via GABAergic system activation, as they can be blocked or reversed by GABAA receptor antagonists. Further work is needed to better understand the general anesthetic properties of melatonin at the molecular, cellular, and systems levels.

Pomegranate juice decreases amyloid load and improves behavior in a mouse model of Alzheimer's disease

Although there are no proven ways to delay onset or slow progression of Alzheimer's disease (AD), studies suggest that diet can affect risk. Pomegranates contain very high levels of antioxidant polyphenolic substances as compared to other fruits and vegetables. Polyphenols have been shown to be neuroprotective in different model systems. We asked whether dietary supplementation with pomegranate juice (PJ) would influence behavior and AD-like pathology in a transgenic mouse model. Transgenic mice (APP(sw)/Tg2576) received either PJ or sugar water control from 6 to 12.5 months of age. PJ-treated mice learned water maze tasks more quickly and swam faster than controls. Mice treated with PJ had significantly less (approximately 50%) accumulation of soluble Abeta42 and amyloid deposition in the hippocampus as compared to control mice. These results suggest that further studies to validate and determine the mechanism of these effects, as well as whether substances in PJ may be useful in AD, should be considered.

Characteristics of lysophosphatidylcholine-induced Ca2+ response in human neuroblastoma SH-SY5Y cells

Lysophosphatidylcholine (LPC) is an important bioactive lipid. In the nervous system, elevated levels of LPC have been shown to produce demyelination. In the present study, we examined the effect of exogenous LPC on intracellular Ca2+ mobilization in human neuroblastoma SH-SY5Y cells. In Ca2+-containing medium, introduction of LPC induced a steady rise in cytosolic Ca2+ levels ([Ca2+]i) in a dose-dependent manner, and this rise was provoked by LPC itself, not by its hydrolysis product produced by lysophospholipase. The increase in [Ca2+]i was reduced by 36% by removal of extracellular Ca2+, while preincubation of the cells with verapamil, an L-type Ca2+ channel blocker, inhibited the response by 23%, part of the Ca2+ influx. Conversely, Ni2+, which inhibits the Na+-Ca2+ exchanger, or Na+-deprivation did not affect LPC-induced Ca2+ influx. In Ca2+-free medium, depletion of Ca2+ stores in the endoplasmic reticulum (ER) by thapsigargin, an ER Ca2+-ATPase inhibitor, abolished the Ca2+ increase. Moreover, LPC-induced [Ca2+]i increase was fully blocked by ruthenium red and procaine, inhibitors of ryanodine receptor (RyR), but was not affected by 2-aminoethoxydiphenyl borate, an inhibitor of inositol triphosphate receptor, or by pertussis toxin, a G(i/o) protein inhibitor. Combined treatment with verapamil plus thapsigargin markedly inhibited but did not abolish the LPC-induced Ca2+ response. These findings indicate that LPC-induced [Ca2+]i increase depends on both external Ca2+ influx and Ca2+ release from ER Ca2+ stores, in which L-type Ca2+ channels and RyRs may be involved. However, in digitonin-permeabilized SH-SY5Y cells, LPC could not induce any [Ca2+]i increase in Ca2+-free medium, suggesting that LPC may act indirectly on RyRs of ER.

Neuroprotective effects of behavioural training and nicotine on age-related deficits in spatial learning

Studies in humans and animals show a clear decline in spatial memory with age and several approaches have been adopted to alleviate this impairment. The purpose of our review is to assess the studies that have suggested the possible neuroprotective actions of behavioural training and nicotine-applied both independently and in conjunction-on age-related deficits in spatial learning. Both spatial pretraining and nonspatial experiences influence an animal's performance in spatial tasks. In aged rats, the experience of training in the water maze task increases the number of newly generated neurons in the hippocampus. The neuroprotective effects of nicotine have been demonstrated in both in-vitro and in-vivo models, although the molecular mechanisms underlying these actions are not yet fully understood. It had been concluded in different studies that nicotine can improve, impair or have no effect on performance in the water maze. Neurobiological data also suggest an interaction between nicotine and prior experience in complex tasks, although few studies have raised the question of whether nicotine treatment and training in spatial tasks may contribute in an interactive manner to alleviate spatial cognition impairment associated with the ageing process. Different findings suggest that past experience could be a confounding variable in longitudinal studies that aim to evaluate the neuroprotective effects of nicotine on age-related deficits in spatial learning.

Synthesis, antioxidant activity and structure-activity relationships for a new series of 2-(N-acylaminoethyl)indoles with melatonin-like cytoprotective activity

5-Methoxy-2-(N-acetylaminoethyl)indole (5d), a melatonin analogue derived from the transposition of the acetylaminoethyl side chain from C3 to C2 of the indole nucleus, had been previously characterized as a low affinity antagonist at MT1 and MT2 membrane receptors; this molecule is endowed with good in vitro antioxidant and cytoprotective potency in rat cerebellar cell cultures, comparable to or better than those of melatonin. In order to further investigate the role of structure-antioxidant activity relationships in cytoprotection, the structure of 5d was systematically modulated to design a new series of compounds. The 5-methoxy group was replaced by substituents with different electronic and lipophilic properties and it was moved to a different position on the indole ring. Other modifications of the lead structure involved the methylation of the indole nitrogen or its replacement by a sulfur atom. The side chain was also modified either increasing its lipophilicity or introducing an ionisable acid group. The antioxidant activity of this set of compounds was evaluated by the ABTS and conjugated dienes (CD) assays, while their cytoprotection was evaluated against kainate-induced cytotoxicity in cultured cerebellar neurons. In both antioxidant assays, the shift of the 5-methoxy group to the 4-position of the indole nucleus led to the most active radical scavenger (9), more potent than the parent compound and melatonin in the antioxidant tests, but much less effective as a cytoprotectant. Sharp structure-activity relationships were registered for cytoprotection, where the maintenance of the 5-alkoxy-2-(N-acylaminoethyl)indole scaffold appeared as the key feature to confer both antioxidant and cytoprotective activity to the structure. Some derivatives of the set, however, together with the most potent 5d, maintained a significant antioxidant and cytoprotective effect and could be employed as tools for in vivo pharmacological investigations on neuroprotective efficacy of melatonin-related indoles.

Beneficial effects of melatonin in experimental models of Alzheimer disease

Alzheimer's disease (AD), a progressive degenerative disorder, is characterized by the presence of amyloid deposits, neurofibrillary tangles and neuron loss. Emerging evidence indicates that antioxidants could be useful either for the prevention or treatment of AD. It has been shown that melatonin is a potent antioxidant and free radical scavenger. Additionally, melatonin stimulates several antioxidative enzymes and improves mitochondrial energy metabolism. These findings led us to study amyloid precursor protein transgenic mice, ovariectomized rats, and pheochromocytoma and astroglioma cell lines, to observe whether melatonin had any effect on Alzheimer's symptoms or pathological changes. We found that melatonin had many beneficial effects in experimental models of AD, including improvement of cognitive function, anti-oxidative injury, anti-apoptosis, inhibition of beta-amyloid (Abeta) deposition and Abeta fiber formation. Several groups have shown that melatonin has an inhibitory effect on tau protein hyperphosphorylation. These actions may potentially slow down or stop the progression of dementia.

Early melatonin supplementation alleviates oxidative stress in a transgenic mouse model of Alzheimer's disease

Multiple lines of evidence demonstrated that increased brain oxidative stress is a key feature of Alzheimer's disease (AD). Melatonin is a potent endogenous antioxidant and free radical scavenger. A transgenic mouse model for AD mimics the accumulation of senile plaques, neuronal loss, and memory impairment. Four-month-old transgenic mice were administrated melatonin at 10 mg/kg for 4 months. We investigated the long-term influence of melatonin on these mice before amyloid plaques were deposited. We found an increase in the levels of brain thiobarbituric acid-reactive substances (TBARS) and a decrease in glutathione (GSH) content, as well as accelerated upregulation of the apoptotic-related factors, such as Bax, caspase-3, and prostate apoptosis response-4 (Par-4) in transgenic mice, but not in wild-type (WT) littermates. Significantly, the increase in TBARS levels, reduction in superoxide dismutase activity, and GSH content were reinstated by melatonin. In addition, transgenic mice administered melatonin (10 mg/kg) showed a significant reduction in upregulated expression of Bax, caspase-3 and Par-4, indicating inhibited triggering of neuronal apoptosis. These results supported the hypothesis that oxidative stress was an early event in AD pathogenesis and that antioxidant therapy may be beneficial only if given at this stage of the disease process. In sharp contrast to conventional antioxidants, melatonin crosses the blood-brain barrier, is relatively devoid of toxicity, and constitutes a potential therapeutic candidate in AD treatment.

Maternal dietary supplementation with pomegranate juice is neuroprotective in an animal model of neonatal hypoxic-ischemic brain injury

Neonatal hypoxic-ischemic brain injury remains a significant cause of morbidity and mortality and lacks effective therapies for prevention and treatment. Recently, interest in the biology of polyphenol compounds has led to the discovery that dietary supplementation with foods rich in polyphenols (e.g. blueberries, green tea extract) provides neuroprotection in adult animal models of ischemia and Alzheimer's disease. We sought to determine whether protection of the neonatal brain against a hypoxic-ischemic insult could be attained through supplementation of the maternal diet with pomegranate juice, notable for its high polyphenol content. Mouse dams were provided ad libitum access to drinking water with pomegranate juice, at one of three doses, as well as plain water, sugar water, and vitamin C water controls during the last third of pregnancy and throughout the duration of litter suckling. At postnatal day 7, pups underwent unilateral carotid ligation followed by exposure to 8% oxygen for 45 min. Brain injury was assessed histologically after 1 wk (percentage of tissue area loss) and biochemically after 24 h (caspase-3 activity). Dietary supplementation with pomegranate juice resulted in markedly decreased brain tissue loss (>60%) in all three brain regions assessed, with the highest pomegranate juice dose having greatest significance (p < or = 0.0001). Pomegranate juice also diminished caspase-3 activation by 84% in the hippocampus and 64% in the cortex. Ellagic acid, a polyphenolic component in pomegranate juice, was detected in plasma from treated but not control pups. These results demonstrate that maternal dietary supplementation with pomegranate juice is neuroprotective for the neonatal brain.

Nanotechnology approaches for the regeneration and neuroprotection of the central nervous system

Nanotechnology is the science and engineering concerned with the design, synthesis, and characterization of materials and devices that have a functional organization in at least 1 dimension on the nanometer (ie, one-billionth of a meter) scale. The ability to manipulate and control engineered self-assembling (ie, self-organizing) substrates at these scales produces macroscopic physical and/or chemical properties in the bulk material not possessed by the constituent building block molecules alone. This in turn results in a degree of functional integration between the engineered substrates and cellular or physiological systems not previously attainable. Applied nanotechnology aimed at the regeneration and neuroprotection of the central nervous system (CNS) will significantly benefit from basic nanotechnology research conducted in parallel with advances in cell biology, neurophysiology, and neuropathology. Ultimately the goal is to develop novel technologies that directly or indirectly aid in providing neuroprotection and/or a permissive environment and active signaling cues for guided axon growth. In some cases, it is expected that the neurosurgeon will be required to administer these substrates to the patient. As such, in order for nanotechnology applications directed toward neurological disorders to develop to their fullest potential, it will be important for neuroscientists, neurosurgeons, and neurologists to participate and contribute to the scientific process alongside physical science and engineering colleagues. This review will focus on emerging clinical applications aimed at the regeneration and neuroprotection of the injured CNS, and discuss other platform technologies that have a significant potential for being adapted for clinical neuroscience applications.

Transplantation of carotid body cells in the treatment of neurological disorders

Laboratory and clinical studies have shown that intracerebral transplantation of carotid body (CB) cells ameliorate Parkinsonian deficits. The recent clinical study by Arjona and colleagues indicated that CB autograft transplantation is a relatively simple, safe, and viable treatment for PD patients. In particular, Espejo and colleagues demonstrated that the therapeutic efficacy of intracerebral transplantation of the CB in PD was likely obtained through secretion of neurotrophic factors rather than the local release of dopamine, which suggests it possible and reasonable to extend the use of the CB as an efficacious graft source for neural transplantation. Thus, we transplanted CB cell suspensions into the ischemic penumbra within 1h after stroke surgery. The results revealed that CB transplantation also significantly reduced stroke-induced behavioral deficits and cerebral infarction. In this review, we focus on summarizing the physiological properties of the CB related to transplantation, describing briefly possible mechanisms responsible for the effect of CB transplantation, and introducing recent studies of the CB as a donor source for neural transplantation.

Neurotoxins and neurotoxic species implicated in neurodegeneration

Neurotoxins, in the general sense, represent novel chemical structures which when administered in vivo or in vitro, are capable of producing neuronal damage or neurodegeneration--with some degree of specificity relating to neuronal phenotype or populations of neurons with specific characteristics (i.e., receptor type, ion channel type, astrocyte-dependence, etc.). The broader term 'neurotoxin' includes this categorization but extends the term to include intra- or extracellular mediators involved in the neurodegenerative event, including necrotic and apoptotic factors. Moreover, as it is recognized that astrocytes are essential supportive satellite cells for neurons, and because damage to these cells ultimately affects neuronal function, the term 'neurotoxin' might reasonably be extended to include those chemical species which also adversely affect astrocytes. This review is intended to highlight developments that have occurred in the field of 'neurotoxins' during the past 5 years, including MPTP/MPP+, 6-hydroxydopamine (6-OHDA), methamphetamine; salsolinol; leukoaminochrome-o-semiquinone; rotenone; iron; paraquat; HPP+; veratridine; soman; glutamate; kainate; 3-nitropropionic acid; peroxynitrite anion; and metals (copper, manganese, lead, mercury). Neurotoxins represent tools to help elucidate intra- and extra-cellular processes involved in neuronal necrosis and apoptosis, so that drugs can be developed towards targets that interrupt the processes leading towards neuronal death.

Nicotine inhibits ethanol-induced toxicity in cultured cerebral cortical cells

The high incidence of smoking among alcoholics may be partially due to nicotine's ability to counteract some of the adverse effects of ethanol on motor coordination and/or cognitive functions. Neuroprotective effects of nicotine on ethanol-induced toxicity in cerebellar granular cells have been observed. In this study, we sought to determine whether similar protection is observed in neocortical cells and if so, what specific nicotinic receptor subtypes may be mediating the actions of nicotine. Primary cultures of neocortical cells were prepared from 20-day embryos obtained from time-pregnant Sprague-Dawley rats. Cells were cultured for 10 days and were then exposed for 3 days to various concentrations of ethanol with and without pretreatment with nicotine and nicotinic antagonists. Cellular toxicity was evaluated by measuring the lactate dehydrogenase level. Administration of ethanol (10-100 mM) resulted in a dose-dependent toxicity. Pretreatment with nicotine 5-20 microM resulted in a dose-dependent protection against ethanol-induced toxicity. The effects of nicotine were blocked by pretreatment with nicotinic antagonists such as mecamylamine (1-20 microM), dihydro-beta-erythroidine (DHBE) 50 nM-1.0 microM and methyllycaconitine (MLA) 5 nM-1 microM in a dose-dependent manner. Compared to previous studies, higher ethanol concentrations were required to induce toxicity in neocortical vs cerebellar granule cells. Moreover, the effects of nicotine in the neocortical cells were blocked by lower concentrations of MLA, but higher concentrations of DHBE compared to cerebellar cells. Collectively, the results suggest differential sensitivity of various neuronal populations to the toxic effect of ethanol. Furthermore, protective effects of nicotine against alcohol in various regions appear to be mediated by different nicotinic receptor subtypes. The neuroprotective effect of nicotine against ethanol-induced toxicity may be a contributing factor to the high incidence of smoking among alcoholics.